1. Technical Field
The disclosure relates to a transmission case provided in an automatic transmission and so on.
2. Description of Related Art
As disclosed in Japanese Patent Application Publication No. 2013-194906 (JP 2013-194906 A), in an automatic transmission mounted on a vehicle, a transmission is housed inside a transmission case. Also, in the transmission case, a through hole is provided, in which a power transmission shaft is inserted, and a peripheral portion of the through hole is structured as a bearing portion that supports the power transmission shaft so that the power transmission shaft is able to rotate. Further, a transmission cover is attached to the transmission case. To be specific, in outer edge portions of the transmission case and the transmission cover, fitting portions are formed, respectively, each having a flat mating surface. In a plurality of locations in the fitting portions, fastening portions having bolt holes are provided. When attaching the transmission cover to the transmission case, the fitting portions are superimposed on each other, and, in a state where positions of the bolt holes are aligned with one another, bolts are inserted into these bolt holes. Thus, the fitting portions are fastened to each other.
Also, in the power transmission shaft, gears for power transmission are provided. Therefore, the transmission case is required to have high strength in order to be able to endure radial force and thrust force generated when power is transmitted through these gears. In JP 2013-194906 A, ribs are provided between the bearing portion of the transmission case and the plurality of fastening portions in the vicinity of the bearing portion, respectively, thereby giving the transmission case high strength.